THE DETERMINATION OF SODIUM AND POTASSIUM. 
By F. H. McCRUDDEN anp C. S. SARGENT. 
(From the Robert B. Brigham Hospital, Boston.) 
(Received for publication, November 26, 1917.) 
Sodium and potassium can be separated from other com- 
pounds as NaCl-+ KCl, and the amount of each calculated 
from the chlorine content of a known weight of the mixture. 
NaCl ++ KCl = 8! 
35.45 
NaCl + 33 KCl = H? 
35.45 
58.50 
Though the possibilities of error are great, the method is, never- 
theless, practicable. 
The percentage error in NaCl: percentage error in C] = 
ie 
7 NaCl ANaCl.H 
AHA TL ANaCl 
tO 
(ANaCl and AH being the absolute errors). 
Solving the first two equations: 
35.45 
Lae 
74.56 
NaCl = 395 35.45 
58.50 74.56 
Differentiating NaCl with respect to H: 
5NaCl _ 1 
su ~ 35.45 38.45 
58.50 74.56 
Substituting these values, we get as percentage error in sodium 
1 Sum. 
2 Halide. 
239 
